A song Ed Sheeran co-wrote for Faith Hill and Tim McGraw is the subject of the latest copyright infringement lawsuit.

The superstar pair released the tune The Rest of Our Life last October, with British singing sensation Ed credited as co-writer. However, Australian pair Sean Carey and Beau Golden filed a complaint in New York federal court on Wednesday, saying that the song is "blatant copying" of their own 2014 tune When I Found You.

"The copying is, in many instances, verbatim, note-for-note copying of original elements of the Song, and is obvious to the ordinary observer," the complaint states.

Carey and Golden are being represented by Richard Busch, who won a trial for Marvin Gaye's family in their lawsuit over the track Blurred Lines. It's also not Busch's first time taking on Sheeran, as he previously fought the singer in a $20 million copyright lawsuit over his track Photograph. That case ended with a settlement, which saw the two songwriters who sued Sheeran being added to the song credits and receiving a share of its royalties.

This time, Sheeran is named in the lawsuit alongside co-writers Johnny McDaid and Amy Wadge, as well as Sony/ATV, Universal Polygram and WB Music. The complaint also claims that Sony Music employees were well aware of the copying of When I Found You.

"It very well may have been an agent of Sony Music Entertainment who provided the other defendants herein with access to the Song," the complaint reads.

When I Found You was initially released in Australia by co-writer and recording artist Jasmine Rae. In the complaint, Busch also points out that Rae is in a relationship with Sony marketing manager Tim Holland, who was tasked with promoting the McGraw/Hill song.

"(Holland was) instrumental in bringing Plaintiffs' work to the attention of the Defendants and likely provided access to it. Indeed, it strains credibility to believe that it is just a coincidence that the Infringing Song/Infringing Sound Recording, a blatant note for note copy of the Song, was created without Mr. Holland's providing access, when Mr. Holland is the boyfriend of one of the writers of the Song," Busch says in the complaint.

"In support of this position, Plaintiffs allege, upon information and belief, that Mr. Holland presented Plaintiffs' song to Sony Music in an effort to gain exposure for Ms. Rae and promote her work."

Another theory about how the infringement occurred is also listed in the lawsuit, and refers to the fact that Sheeran was touring Australia when When I Found You was a success and frequently being played on local radio stations.

Carey and Golden are seeking $5 million in actual damages plus profits, royalties and an award of attorney's fees, as well as injunctive relief.